Tree nuts

Tree nuts belong to several different botanical families. In Annex IIIa to Directive 2003/89/EC (the labeling directive) the following nuts have been defined; almond, hazelnut, walnut, cashew, pecan nut, Brazil nut, pistachio nut, macadamia nut and Queensland nut.

Nut allergy might include a single species of nut or several different nuts.
Nut proteins from several different nuts have been characterized as allergenic.

Nuts are commonly used for decoration and for the taste in a huge variety of food and food products such as bakery products, confectionaries, bread, chocolate, ice-cream and pesto.

Nuts are also raw material for the processing of oils. Fully refining of oils results in almost complete removal of proteins. In crude (cold-pressed) oils protein residues might be present and such oils could pose a risk for allergic individuals.

Labeling

The presence of specified nuts and products thereof in food products must always be declared, see further in LIVSFS 2004:27 Livsmedelsverkets föreskrifter om märkning och presentation av livsmedel [in Swedish] (see link to the right).

Examples of methods of analysis

Sensitive commercial ELISA test kits are available for analysis of hazelnut, almond and walnuts. The limit of quantification is about 2.5 mg nut/kg, somewhat depending on the matrix.

Several tree nuts can be detected in food samples using rapid methods, based on test strips, which are soaked in an extract of the food or in a swab sample extract. Such tests are only qualitative, i.e. the result is given either as nut is present (positive) or nut is not present (not detected) in the food extract. Positive results need sometimes to be confirmed with quantitative methods. It is very important that qualitative test kits don’t give false negative results.

Nut proteins (almond, hazelnut, walnut, cashew, pecan nut, Brazil nut, pistachio nut and macadamia nut) can be quantified with rocket immuno electrophoresis using specific antibodies to nut proteins. The limit of quantification varies somewhat depending on the nut being analyzed. For hazelnut the limit of quantification is 10 mg hazelnut protein/kg (ppm) and for almond 20 mg almond protein/kg, respectively.

Nuts can be identified with species specific DNA methods. A positive result in a DNA analysis indicates the presence of specific nuts in a sample.

Providers of test kit often have a validation protocol to be submitted with the test kit upon request. Laboratories using commercial assays must establish in house control of limit of detection and limit of quantification in actual matrices even if the test has been validated by the provider.

Allergic reactions to hazelnut / Doses

The lowest dose of hazelnut protein that elicitates an allergic reaction is not known. The concentrations of hazelnut proteins that have been detected in food products causing allergic reactions are listed below. The protein constitutes about 12 percent of the hazelnut.

* Anaphylaxis means that the allergic individual suffers from blood pressure drop, respiratory comprise/cramps in the airways and a systemic reaction, called anaphylactic shock
** Fatal anaphylaxis means that the shock develops to unconsciousness and death

Allergic reaction to Brazil nut / Dose

The lowest dose of Brazil nut protein that elicitates an allergic reaction is not known. The concentrations of Brazil nut proteins that have been detected in food products causing allergic reactions are listed below. The protein constitutes about 14 percent of the Brazil nut.

* Anaphylaxis means that the allergic individual suffers from blood pressure drop, respiratory comprise/cramps in the airways and a systemic reaction, called anaphylactic shock